If they refuse to verify then, if I were you, I'd send them all letters, immediately, Certified RRR, stating that you want your name removed from the accounts, and that effective immediately, you are no longer financially liable for new charges on the accounts.
Make clear in each letter that this is not the first time you are demanding your name be removed from the account. For each letter, state the date and manner in which you first demanded your name be removed from the respective account.
This is just a CYA procedure.